1. Field of the Invention
The present invention relates to an ink set, an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus.
2. Description of the Related Art
As inks used in ink jet recording, generally, dye inks in which water-soluble dyes are dissolved in aqueous medium have been widely used. In recent years, pigment inks formed by dispersing pigments having higher water-fastness and higher lightfastness than dyes in aqueous medium have also been provided. Examples of the pigment inks include a pigment ink formed by dispersing a pigment using a dispersant in an aqueous medium, and a pigment ink having a self-dispersion pigment as a coloring material, the self-dispersion pigment having a hydrophilic group bonded to its surface to facilitate its dispersion, and the self-dispersion pigment being dispersed in an aqueous medium.
In exemplary proposals, a self-dispersion pigment is selected as a coloring material for a black ink used to record characters and drawings on plain paper because it allows achievement of high image density and excellent character quality (Japanese Patent Laid-Open Nos. 2000-198955 and 2001-089688).
Furthermore, as to a pigment ink used to form an image on a special recording medium, such as glossy paper having a coated surface, it has been considered to be effective from the viewpoint of abrasion resistance and glossiness to use a polymer-dispersion pigment as a coloring material, the polymer-dispersion pigment being dispersed using a polymer as a dispersant. Moreover, in recent years, in order to obtain high image quality regardless of the type of recording medium, proposals have been made in which a plurality of pigment inks of different pigment dispersion types are combined. For example, in one proposal, two types of ink, namely, a polymer-dispersion pigment ink in which a polymer-dispersion pigment is used as a coloring material, and a self-dispersion pigment ink in which a self-dispersion pigment is used as a coloring material, are provided in an ink jet recording apparatus to form an image (Japanese Patent Laid-Open No. 2003-213180).